more helpful error message when weave et al die on startup
more helpful error message when weave et al die on startup

Closes #958.

cgvarela/weave,narry/weave,paladin74/weave,dpw/weave,2opremio/weave,ycaihua/weave,awanke/weave,narry/weave,OnePaaS/weave,ycaihua/weave,awanke/weave,aaam/weave,OnePaaS/weave,kidaa/weave,philipz/weave,philipz/weave,achanda/weave,achanda/weave,errordeveloper/weave,errordeveloper/weave,beni55/weave,squaremo/weave,kidaa/weave,bboreham/weave,beni55/weave,n054/weave,paladin74/weave,2opremio/weave,bboreham/weave,awh/weave,n054/weave,bboreham/weave,cgvarela/weave,beni55/weave,weaveworks/weave,cgvarela/weave,errordeveloper/weave,n054/weave,kidaa/weave,paladin74/weave,dpw/weave,BWITS/weave,paladin74/weave,errordeveloper/weave,weaveworks/weave,2opremio/weave,2opremio/weave,weaveworks/weave,squaremo/weave,OnePaaS/weave,paulbellamy/weave,aaam/weave,philipz/weave,paulbellamy/weave,philipz/weave,narry/weave,rade/weave,tomwilkie/weave,paladin74/weave,cgvarela/weave,BWITS/weave,narry/weave,awanke/weave,achanda/weave,BWITS/weave,dpw/weave,awh/weave,tomwilkie/weave,squaremo/weave,errordeveloper/weave,tomwilkie/weave,BWITS/weave,awh/weave,OnePaaS/weave,rade/weave,beni55/weave,aaam/weave,paulbellamy/weave,rade/weave,awh/weave,2opremio/weave,cgvarela/weave,weaveworks/weave,rade/weave,achanda/weave,aaam/weave,BWITS/weave,ycaihua/weave,tomwilkie/weave,dpw/weave,awanke/weave,awanke/weave,rade/weave,achanda/weave,beni55/weave,bboreham/weave,bboreham/weave,n054/weave,narry/weave,kidaa/weave,squaremo/weave,OnePaaS/weave,philipz/weave,paulbellamy/weave,tomwilkie/weave,n054/weave,ycaihua/weave,aaam/weave,squaremo/weave,awh/weave,dpw/weave,ycaihua/weave,kidaa/weave